Cooling/hydrating systems producing fine fluid sprays have been employed in various applications for many years. Such systems typically involve a pressurized fluid, usually water, escaping through a small orifice. The spray droplets produced by a standard nozzle are sufficiently small for agricultural applications, however, in evaporating systems, where a finer spray is required, the pressurized fluid, upon escaping through the small orifice, impinges on a proximate surface (pin jet nozzles). The force of the pressurized stress against the surface causes the fluid to disperse into minute particles creating a localized fog or mist.
Because of the difficulty in precisely cutting the small diameter orifice and delivery channel, prior art nozzles were typically formed from brass and other relatively soft metals. The short delivery channels of the prior art were necessary because of the limitations of metalworking. Cutting a narrow orifice, typically on the order of six one-thousandths of an inch (0.006 inch), was typically done with a pin drill, usually a stationary drill which engages rotating work. The depth which can be achieved with such a metalworking procedure, typically no greater than fifteen one-thousandths of an inch (0.015 inch), is chiefly a function of how well the drill bit can be supported during the metalworking process.
Further, the nature of the metalworking employed to cut the orifice and delivery channel was such that the integrity of the orifice and channel walls was difficult to maintain. The drilling operation was known to gouge and scar the interior surface of the delivery channel and leave an imprecise mouth to the orifice itself. Subsequently, some nozzles were produced in stainless steel, however such nozzles still followed the design of previous nozzles.
Recent developments in the production of nozzle inserts changed the manner in which spray nozzles have been manufactured. U.S. Pat. No. 4,869,430 to Good, describes an improved pin jet nozzle having a delivery channel of greater length, thereby producing better diffusion characteristics. The method of manufacturing provided a delivery channel with interior surface unmarked by metalworking and wherein the orifice had greater integrity. The novel concept of the '430 patent disclosed a delivery channel having the same diameter as the outlet orifice and having a length of at least three times its diameter. A blank base portion was drilled out to accommodate the insertion of an orifice component that was separately prepared. Thus, the blank base was drilled not with a pin drill, but with a drill of approximately sixty-two one-thousandths of an inch (0.062 inch). Because of the great difference in size, and since it was not intended to define an opening in the finished nozzle, this drilling procedure did not require the extreme accuracy of the drilling operation of the prior art.
FIGS. 1 and 2 describe typical spray nozzle assemblies of the prior art. In FIG. 1 the spray nozzle assembly is comprised of four components, nozzle portion 1, piston 2, spring 3 and filter portion 4. The nozzle portion 1 has a threaded exterior portion 7 for receipt in a fluid dispersing system and an internal threaded portion, not shown, for receipt of complementary threaded portion 9 of filter portion 4. Nozzle portion 1 has a cylindrical interior for receipt of piston 2, which piston 2 serves to regulate the amount of fluid through the spray nozzle assembly. Nozzle portion 1 has a fluid exit hole 5, and surface 6 of nozzle portion 1 is machined to mate with piston 2. Perpendicular cross-flow channels are inscribed in surface 6 to create a flow path for the fluid. Filter portion 4 forms a cylindrical interior for receipt of spring 3 and for communicating fluid to nozzle portion 1. The filter, not shown, is in the form of a wire mesh that is formed cylindrically about the external surface of filter portion 4 at point 8. When assembled, spring 3 is seated in filter portion 4, and is compressed against piston 2 to firmly bias piston 2 against surface 6. Fluid under pressure enters the nozzle assembly through filter portion 4, around piston 2, and exits the spray nozzle via the cross-flow channels and exit hole 5. The wire mesh filter of filter portion 4 is sized to block only larger impurities in the fluid, and does not impede smaller impurities which eventually clog exit hole 5. Although the nozzle assembly of FIG. 1 may be dissembled for cleaning, it is extremely difficult and time consuming to clear the impurities from exit hole 5, and consequently, the nozzle assembly is simply discarded.
FIG. 2 discloses a second prior art nozzle assembly that is comprised of a generally cylindrically shaped body 10, nozzle portion 11, and piston 12. Body 10 defines a cylindrical interior chamber 14 extending the length of cylindrical body 10, which chamber 14 provides a flowpath for the fluid. Body 10 has an insertion end 13, which is threaded for receipt in a fluid dispersing system, and a nozzle end for creating a fluid spray, the nozzle end having a circular recess for receiving the nozzle portion 11. Piston 12 is a piece of solid stock of approximately half the length of interior chamber 14, with one end of piston 12 having flow-channels inscribed thereon at 16 to create a flow path for the fluid. Piston 12 is contained within interior chamber 14 of body 10 at one end by nozzle portion 11, and at the other end by rolling over of body 10 at the edges of body 10 at interior chamber 14. Nozzle portion 11 is a circular plate, having an exit hole 15, creating a flow path for the fluid. After insertion of piston 12 in chamber 14, nozzle portion 11 is pressure inserted into a complementary circular recess in body 10. Body 10 and nozzle portion 12 are sized such that the composite surface of body 10 and nozzle portion 12 is smooth. When the spray nozzle assembly is threadably inserted in a fluid dispersing system, fluid pressure impels piston 12 firmly against the interior surface of nozzle portion 11. Fluid flows around piston 12, through the flow channels, and exits through exit hole 5.
However, even with the improved orifices and filters, such prior art nozzles are still subject to blockage due to impurities in the fluid. Under pressure, such impurities frequently lodge in the orifice of nozzle portion 11, and subsequently, the accumulation of impurities completely plugs passage of the fluid. Once plugged, it is highly impractical to clear out the orifice and re-use the nozzle. As a result, the spray nozzle must be replaced. Analysis of plugged nozzles has shown that the accumulation of impurities causing the blocking occurs at the surface of the exit holes in the interior of the nozzle portions.